12

2

Since the nA and Eb show a negative relationship for all specimens, the nA may be useful for evaluating Eb after the start of rapid oxidation (Fig. 3). [H10014]. * The oxidation degree is defined as the ratio of absorbance due to the C=O bond at 1720 cm-1 to that due to the

C-H bond at 1462 cm-1 in infrared absorption spectrum.

Fig. 1 EDM notch depth sizing by Phased Array UT Good accuracy is evaluated for defect depth sizing from shallow to deep defect by advanced Phased Array UT.

Fig. 2 An example of transitions of Oxidation degree (nA) and Elongation at break (Eb)

During the initial period (T), nA and Eb are reasonably stable, but nA decreases with aging time. After such a period, nA continues to decrease, and nA and Eb start to change drastically. It is clarified from these experimental results that there exists a certain antioxidant content that effectively inhibits oxidation.

Defect Tip Echo

EDM notchd=40mm

Defect Tip

Surface

0

10

20

30

40

50

0 10 20 30 40 50

EDM notch depth (mm)

Meas

ured

dept

h b

y P

AU

T(m

m) ● Advance PAUT

● Conventional PAUT

T

Fig. 3 Relationship between Oxidation degree (nA) and Elongation at break (Eb)

For all specimens Eb decreases with an increase in nA. The nA may be useful for evaluating Eb after the start of rapid oxidation. Eb of reference cable specimens was cited from “The final report of the project of assessment of cable aging for nuclear power plants”, JNES-SS-0903, and those specimens were provided from JNES for our chemical analyses.

Project Subjects

Background and Objective

For long-term operation of nuclear power plants, aging of equipment, pipes and instrumentation and elec-trical equipment is an important issue that should be taken into account. It has been expected to develop diagnosis method to detect their aging.

In case of SCC crack appearance, continuous operation or repair of component is selected, following the JSME code “Rules on Fitness-for-Service for Nuclear Power Plants”. Phased array UT was applied to measure the defect depth sizing on several components such as pipe and shrouds, etc. However, it was difficult to measure the defect depth sizing on nickel based alloy welds by conventional UT. Therefore, the development of advanced phased array UT technique is required for nickel based alloy welds.

Long-term integrity of cable insulation was confirmed by tests based on the Technical Report published by the Institute of Electrical Engineers of Japan. Especially, the confirmation of integrity (evaluation of material deterioration) of mechanical properties such as strength and elongation of cable insulation is important since cable insulation is deteriorated due to thermal stress and radiation. Therefore, it is required to establish the effec-tive index to evaluate the combined radiation-thermal deterioration of cable insulating materials.

The objectives of this project are to develop the phased array UT technique for measurement of high accuracy for defect depth sizing and to establish the analysis method to evaluate quantitatively radiation-thermal deterioration of cable insulating materials.

Main results

1. Application of Phased Array UT for crack depth sizing on nickel based alloy weldAdvanced Phased Array UT (PAUT) technique, which combines 3-dimensional Phased Array UT (3-D

PAUT) and 2-dimensional Phased Array UT (2-D), was investigated. 3-D PAUT technique can be controlled by ultrasound beam steering, objective focal points and high power excitation of ultrasound. Advanced Phased Array UT technique was applied to nickel based alloy weld specimen with EDM notches of 5mm to 40mm depth. At first UT conditions were optimized, and then UT examination was carried out. From the experimental results, defect depth sizing accuracy showed good agreement (defect depth accuracy approximately equal to 1mm) (Fig.1). Therefore, high performance of advanced Phased Array UT technique was shown [Q10031].

2. Mechanical strength degradation of cross-linked polyethylene insulation under radiation-thermal accel-erated aging test

Since oxidation seems to be related to material degradation, the samples investigated are three kinds of cross-linked polyethylene sheets with additive antioxidant whose contents were usual, half of usual, and additive-free. These specimens were aged by the irradiation of γ-rays at a dose rate of about 100 Gy/h for various times and temperatures at about 10-30℃ (room temperature, RT), 60℃, and 100℃. Temporal transitions in remaining antioxidant content (nA), and oxidation degree* were evaluated by thermal analyses as well as the elongation at break (Eb) by tensile test. We found the following results; nA decreases below a certain content and the oxidation degree and Eb start to change drastically (Fig. 2). Since the nA and Eb show a negative relationship for all speci-mens, the nA may be useful for evaluating Eb after the start of rapid oxidation (Fig. 3) [H10014].

* The oxidation degree is defined as the ratio of absorbance due to the C=O bond at 1720 cm-1 to that due to the C-H bond at 1462 cm-1 in infrared absorption spectrum.

Deterioration Diagnosis of Instrumentation and Electrical Equipment

02_1Nuclear4_27_2010.indd 12 11/10/03 16:01

13

2

Since the nA and Eb show a negative relationship for all specimens, the nA may be useful for evaluating Eb after the start of rapid oxidation (Fig. 3). [H10014]. * The oxidation degree is defined as the ratio of absorbance due to the C=O bond at 1720 cm-1 to that due to the

C-H bond at 1462 cm-1 in infrared absorption spectrum.

Fig. 1 EDM notch depth sizing by Phased Array UT Good accuracy is evaluated for defect depth sizing from shallow to deep defect by advanced Phased Array UT.

Fig. 2 An example of transitions of Oxidation degree (nA) and Elongation at break (Eb)

During the initial period (T), nA and Eb are reasonably stable, but nA decreases with aging time. After such a period, nA continues to decrease, and nA and Eb start to change drastically. It is clarified from these experimental results that there exists a certain antioxidant content that effectively inhibits oxidation.

Defect Tip Echo

EDM notchd=40mm

Defect Tip

Surface

0

10

20

30

40

50

0 10 20 30 40 50

EDM notch depth (mm)

Meas

ured

dept

h b

y P

AU

T(m

m) ● Advance PAUT

● Conventional PAUT

T

Fig. 3 Relationship between Oxidation degree (nA) and Elongation at break (Eb)

For all specimens Eb decreases with an increase in nA. The nA may be useful for evaluating Eb after the start of rapid oxidation. Eb of reference cable specimens was cited from “The final report of the project of assessment of cable aging for nuclear power plants”, JNES-SS-0903, and those specimens were provided from JNES for our chemical analyses.

2

Since the nA and Eb show a negative relationship for all specimens, the nA may be useful for evaluating Eb after the start of rapid oxidation (Fig. 3). [H10014]. * The oxidation degree is defined as the ratio of absorbance due to the C=O bond at 1720 cm-1 to that due to the

C-H bond at 1462 cm-1 in infrared absorption spectrum.

Fig. 1 EDM notch depth sizing by Phased Array UT Good accuracy is evaluated for defect depth sizing from shallow to deep defect by advanced Phased Array UT.

Fig. 2 An example of transitions of Oxidation degree (nA) and Elongation at break (Eb)

During the initial period (T), nA and Eb are reasonably stable, but nA decreases with aging time. After such a period, nA continues to decrease, and nA and Eb start to change drastically. It is clarified from these experimental results that there exists a certain antioxidant content that effectively inhibits oxidation.

Defect Tip Echo

EDM notchd=40mm

Defect Tip

Surface

0

10

20

30

40

50

0 10 20 30 40 50

EDM notch depth (mm)

Meas

ured

dept

h b

y P

AU

T(m

m) ● Advance PAUT

● Conventional PAUT

T

Fig. 3 Relationship between Oxidation degree (nA) and Elongation at break (Eb)

For all specimens Eb decreases with an increase in nA. The nA may be useful for evaluating Eb after the start of rapid oxidation. Eb of reference cable specimens was cited from “The final report of the project of assessment of cable aging for nuclear power plants”, JNES-SS-0903, and those specimens were provided from JNES for our chemical analyses.

2

Since the nA and Eb show a negative relationship for all specimens, the nA may be useful for evaluating Eb after the start of rapid oxidation (Fig. 3). [H10014]. * The oxidation degree is defined as the ratio of absorbance due to the C=O bond at 1720 cm-1 to that due to the

C-H bond at 1462 cm-1 in infrared absorption spectrum.

Fig. 1 EDM notch depth sizing by Phased Array UT Good accuracy is evaluated for defect depth sizing from shallow to deep defect by advanced Phased Array UT.

Fig. 2 An example of transitions of Oxidation degree (nA) and Elongation at break (Eb)

During the initial period (T), nA and Eb are reasonably stable, but nA decreases with aging time. After such a period, nA continues to decrease, and nA and Eb start to change drastically. It is clarified from these experimental results that there exists a certain antioxidant content that effectively inhibits oxidation.

Defect Tip Echo

EDM notchd=40mm

Defect Tip

Surface

0

10

20

30

40

50

0 10 20 30 40 50

EDM notch depth (mm)

Meas

ured

dept

h b

y P

AU

T(m

m) ● Advance PAUT

● Conventional PAUT

T

Fig. 3 Relationship between Oxidation degree (nA) and Elongation at break (Eb)

For all specimens Eb decreases with an increase in nA. The nA may be useful for evaluating Eb after the start of rapid oxidation. Eb of reference cable specimens was cited from “The final report of the project of assessment of cable aging for nuclear power plants”, JNES-SS-0903, and those specimens were provided from JNES for our chemical analyses.

Nuclear Technology

Fig. 2 An example of transitions of Oxidation degree (nA) and Elongation at break (Eb)

During the initial period (T), nA and Eb are reasonably stable, but nA decreases with aging time. After such a period, nA continues to decrease, and nA and Eb start to change drastically. It is clarified from these experimental results that there exists a certain antioxidant content that effectively inhibits oxidation.

Fig. 3 Relationship between Oxidation degree (nA) and Elongation at break (Eb)

For all specimens Eb decreases with an increase in nA. The nA may be useful for evaluating Eb after the start of rapid oxidation. Eb of reference cable specimens was cited from “The final report of the project of assessment of cable aging for nuclear power plants”, JNES-SS-0903, and those speci-mens were provided from JNES for our chemical analyses.

Fig. 1　EDM notch depth sizing by Phased Array UTGood accuracy is evaluated for defect depth sizing from shallow to deep defect by advanced Phased Array UT.

02_1Nuclear4_27_2010.indd 13 11/10/03 16:01